Work in our laboratory showed that Nerve Growth Factor (NGF) injections in newborn rodents prevent the neurotoxic effects of 66- hydroxydopamine (6-OHDA) treatment and lead to a 30-fold increase in sympathetic ganglion volume after 4 weeks. This suggests that NGF may interact significanty with ganglion cell perikaryal plasma membranes as well as on terminals in peripheral end organs as has been proposed by others. Preliminary experiments with I125-NGF support th perikaryal binding hypothesis and are being carried out in greater detail. Another peripheral effect of NGF when given alone or with 6-OHDA is a striking increase in the number of mast cells. In vitro studies are being carried out to determine whether this is a specific NGF effect on fully differentiated mast cells. In the CNS, intracerebral 6-OHDA injections cause abnormal EEG patterns in young rodents; this effect can apparently be prevented by concurrent NGF treatment, suggesting a central protective effect of NGF whose mechanism is being explored in detail. The distribution of adrenergic fibers and terminals in the hypothalamus and limbic system of the primate is being examined immunofluorescently, and autoradiographic experiments to determine the extent of retrograde axonal transport of I125-NGF following intracerebral injection into adrenergic terminal fields are under way. Bibliographic references: L.W. Swanson and W.M. Cowan: A note on the connections and development of the nucleus accumbens. Brain Research, 92:324-330, 1975. L.W. Swanson and W.M. Cowan: The efferent connections of the suprachiasmatic nucleus of the hypothalamus. J. Comp. Neurol., 160:1-12, 1975.